1. Field of the Invention
The invention is based on a throttle assembly for a flowing medium such as an air flow in an internal combustion engine.
2. Description of the Prior Art
In one known throttle assembly for controlling the idling air quantity for an internal combustion engine (German Patent Disclosure DE 38 01 084 A1), the outer of the coaxially disposed throttle devices is embodied as a housing pot, which protrudes into a bypass line and has flow windows, disposed diametrically in the cup jacket, that are congruent with the inside cross section of the bypass line. The inner throttle device is embodied in the form of a tubular segment with one flow window in the tube segment, and with its circumference it protrudes quite close to the inner wall of the cup jacket. The inner throttle device is rotated by a control motor, and its flow window is made to overlap more or less with one of the flow windows in the cup jacket, thereby uncovering the flow window in the cup jacket to a greater or lesser extent. The rotation of the inner throttle device is effected counter to the force of a restoring spring, embodied for instance as a spiral spring, which when the control motor is not activated presses the inner throttle device against a stop.
The throttle assembly of the invention has the advantage that because of the conical embodiment of the two concentrically disposed throttle devices and because of the axial relative displaceability of the two throttle devices in the closing region, it closes completely tightly on the one hand without even the least leakage flows, and on the other, over the entire adjusting range, it runs smoothly because the friction between the throttle devices is minimized and thus requires only slight adjusting forces, which has an advantageous effect on the power and size of an electric control motor for the one throttle device. Because of the reduced friction between the throttle devices, the wear of the throttle devices drops as well, thus lengthening the service life of the throttle assembly.
The size of the flow windows in the throttle devices can be selected arbitrarily, so that by replacing one of the two throttle devices by another with a different window size, the control characteristic curve of the throttle assembly can be adapted very easily to a given application.
Because of the conicity and displaceability of the throttle devices, self-cleaning of the throttle assembly can be achieved in a simple way; in a separate cleaning phase in the closing position of the throttle assembly, one of the cones is set into an oscillating pivoting motion with a small pivoting range. As a result, particles of dust, soot or dirt deposited between the throttle devices are removed.
All the components of the throttle assembly can be made from plastic, making the throttle assembly lightweight and economical to produce. Major production variations that occur in plastic injection molding do not cause leakage of the throttle assembly in the closing direction, making postmachining of the plastic parts unnecessary.
The throttle assembly of the invention can be used to control the air and combustion mixture or for recirculating exhaust gas in internal combustion engines. The throttle assembly can be inserted directly into the air intake tube, for instance, or into the inlet manifold of the engine.
In a preferred embodiment of the invention, the displacement means have a stop and a counterpart stop cooperating with it, each of which is disposed on one of the cones, and a spring element that presses the stop and counterpart stop against one another in the axial direction of the cones. Between the stop and the counterpart stop, at least one axially protruding plunger member and at least one axially set-back receiving member corresponding with it are provided, of which one is disposed on the stop and one on the counterpart stop in such a way that in the closing region of the throttle assembly, the plunger member plunges into the receiving member. As a result of this structural design, a displacement means for the cones in the closing region of the throttle assembly is created in a simple way, and at the same time the friction between the cones outside the closing region is kept slight; this is because in the rest of the adjusting region, the plunger members, limited in number for instance to three, offset by 120xc2x0 circumferentially from one another, rest on the stop or the counterpart stop. By rounding off the face ends of the plunger members, the friction still existing between the cones is limited to the bearing points of the plunger members; the frictional force is brought to bear by the spring element of a compression spring. In this adjustment range, there is a gap spacing between the jacket faces of the two cones, so that no friction is generated there.
To achieve a replicable control characteristic curve of the throttle assembly over the adjusting path of the throttle devices, at least one cone, in an advantageous embodiment of the invention, has a sealing ring, surrounding the flow window, on its jacket face oriented toward the other cone. By means of this sealing ring, which rests on the jacket face, oriented toward it, of the other cone without significant friction, it is possible, when the flow windows of the cones have been made to overlap partially, to prevent the flow of secondary air flows through the gap between jacket faces, which would cause an uncontrollable imprecision of the control characteristic curve.
In advantageous embodiment of the invention, a ring seal is disposed on one of the ends of the two cones, between the faces of the cones oriented toward one another, and is secured to one of the cone jackets. By means of this ring seal, when the throttle assembly is disposed in the fuel preparation system of an internal combustion engine, damage to the throttle assembly from backfiring is averted.
In an advantageous embodiment of the invention, an electric control motor with a power take-off shaft is disposed in the housing; the power take-off shaft is coupled to the rotatable, axially displaceable inner cone via an intermediate gear. Because the control motor is disposed in the housing itself, it is bathed by flowing medium, as a result of which good heat dissipation of the heat losses produced in the control motor is achieved. The heat dissipation can be improved still further if in a further embodiment of the invention, fins or other axial protrusions are provided on the motor housing received in the housing 11 and can be used simultaneously for laminarizing the flow of the medium.
In an advantageous embodiment of the invention, the housing is embodied in two parts and has two flow windows that can be put together in a plane oriented transversely to the housing axis. One housing part contains one of the housing openings forming the inlet and the outlet and also contains the motor housing, while the other housing part has the other housing opening and the outer cone of the two cones. This structural design makes it substantially easier to insert the cones, electric control motor and gear into the housing. The two housing parts are joined together by a simple joining process, by means of snap fastener elements or ultrasonic welding or other connecting means or processes. Furthermore, the possibility is created of placing an air filter or an element for laminarizing the flowing medium, such as a slotted disk, in the connecting plane of the two housing parts.
In an advantageous embodiment of the invention, the cone communicating with the housing opening forming the inlet is embodied as a lattice structure comprising two axially spaced-apart rings and ribs joining the rings together; and the fields in the cone jacket that are enclosed by the rings and ribs, with the exception of at least one field forming the flow window, are closed by a flexible layer of a sealing material. Because of the vacuum created in the closing region of the throttle assembly in the cone that communicates with the inlet, the flexible layer bulges and increases its spacing from the jacket face of the other cone, thus further reducing the friction between the cones. With this structural design, the flexible layers of sealing material form a seal between the jacket faces of the two cones over the entire adjusting range, so that an encompassing seal around the flow windows of the cones can be dispensed with.